Prostaglandins play a major role in the inflammation process and the inhibition of prostaglandin production, especially production of PGG2, PGH2 and PGE2, has been a common target of antiinflammatory drug discovery. However, common non-steroidal antiinflammatory drugs (NSAIDs) that are active in reducing the prostaglandin-induced pain and swelling associated with the inflammation process are also active in affecting other prostaglandin-regulated processes not associated with the inflammation process. Thus, use of high doses of most common NSAIDs can produce severe side effects, including life threatening ulcers, which limit their therapeutic potential. An alternative to NSAIDs is the use of corticosteroids, which have even more drastic side effects, especially when long term therapy is involved.
NSAIDs prevent the production of prostaglandins by inhibiting enzymes in the human arachidonic acid/prostaglandin pathway. The expression of cyclooxygenase-2 (COX-2) is specifically induced in the pathological conditions such as inflammation, pain, and cancer, and is involved in the generation and maintenance of these conditions. According to the line, a series of drugs called coxibs such as celecoxib, rofecoxib, valdecoxib, parecoxib, and etoricoxib have been developed.
Coxib-drugs are useful for the treatment of diseases mediated by cyclooxygenase-2, such as inflammation, pain, cancer, fever, osteoarthritis, rheumatoid arthritis, migraine, neurodegenerative diseases, cardiovascular disease, osteoporosis, asthma, lupus and psoriasis, dysmenorrhea, premature labor, gout, ankylosing spondylitis, bursitis, heat burn, sprain, and contusion (non-patent literature 1).
The benzopyran, naphtopyran, dihydroquinoline, benzothiopyran and dihydronapthalene derivatives, represented by the formula (I) or formula (I′) in this invention are disclosed in the patent literature 1, and preferably selectively inhibit cyclooxygenase-2 over cyclooxygenase-1. Among them, the benzopyran derivative, for example, affords more potent analgesia and more rapid onset of effect than ibuprofen which is the first choice among the conventional drugs. Furthermore it has been confirmed in the preclinical studies that the benzopyran derivatives have lower renal problems which are a matter of concern in conventional COX-2 inhibitors and NSAIDs.